1. Field of the Invention
This invention relates generally to pulley drive systems and more particularly to a high strength drive system including a plurality of nodules attached to a coined cable to provide positive rotary drive engagement with a suitably constructed pulley, sheave or sprocket.
2. Description of the Prior Art
Drive systems are used where it is desirable to couple two or more rotary members together for common rotation. Types of drive systems found in the prior art include the V-belt and pulley drive system, the chain and sprocket drive system and the flat belt and sheave drive system.
Every drive system found in the prior art has its own particular strengths and weaknesses which makes it suitable for certain applications but not for others. For instance, drive chain and sprocket systems are very well suited for heavy duty, high torque drive applications, but are not well suited for high speed usage because of the pitch variations caused by excessive wear produced in linkage joints at high RPM's. The V-belt drive system is well suited for high speed applications but not so well suited heavy duty, high torque jobs due to possible belt slippage. A solution suggested by the prior art as to the problem of producing a drive system that both has high load drive capabilities and which may be run at high RPM's is the "silent chain" or "toothed belt" system. Unfortunately, the silent chain is subject to excessive and premature wear and is quite costly to manufacture.
Most drive systems found in the prior art are suitable only for applications where the rotary members to be driven have parallel axes of rotation. This is certainly true in the case of drive chains which have only a very limited ability to twist out of a single plane of rotation and to lesser extent with V-belts which also resist such twisting.
Drive systems such as those disclosed by C. H. Davids in U.S. Pat. No. 538,222 and by G. F. Bahr in U.S. Pat. No. 2,856,752 were developed to overcome some of the limitations found in other prior art drive systems. Both Davids and Bahr disclose bead chain drive systems including a chain consisting of a plurality of beads loosely connected by short links and sheaves having grooves and/or pockets formed about their curved periphery for engagement with the beads in the chain. The bead chain drive systems found in the prior art overcome many of the previously discussed inadequacies of prior art drive systems in that they are relatively inexpensive to manufacture and may drive rotary members whose planes of rotation are not coincident. However, bead chains found in the prior art are still subject to excessive wear at high RPM's and are not suitable for heavy duty drive applications. In fact, they are only suitable for very light duty drive applications.
Thus, the prior art does not provide a single drive system which combines the advantages of inexpensiveness, high RPM durability, high load drive capabilities, constant and accurate drive pitch characteristics and the ability to simultaneously drive rotary members lying in several planes of rotation.